They found a way to make tobacco produce a protein that can be used to make a nasal vaccine against norovirus, which causes diarrhea and vomiting, especially on cruise ships, in restaurants, schools and on military bases.

"Under appropriate medical care it is not life-threatening. It is just very, very inconvenient," Charles Arntzen, a plant biologist at Arizona State University, told a news conference at a meeting of the American Chemical Society.

The U.S. Centers for Disease Control and Prevention estimates that 23 million cases a year of acute gastroenteritis -- stomach and intestinal upset -- are due to norovirus, also known as Norwalk virus.

Arntzen and colleagues used a genetically engineered plant virus called the tobacco mosaic virus to start their vaccine.

"We force it to make the protein which is the vaccine against norovirus," Arntzen told the news conference. "We call them nanoparticle vaccines because the protein we produce in our tobacco plant self-assembles into a little round ball."

The immune system recognizes this ball, called a virus-like particle or a capsid, as if it were a virus and attacks it, Arntzen said. "It is empty. It cannot cause disease," he said.

Tests have suggested the vaccine would work better in the nose than taken orally, probably because immune cells in the nasal passages are more inclined to take up the vaccine.

PREPARING TESTS

Arntzen said his team has U.S. National Institutes of Health support for a clinical trial in people. "But we have been waiting until we can get the best formulation," he said.

ImmuneRegen BioSciences, Inc., a subsidiary of IR BioSciences Holdings Inc, said on Tuesday it had a collaborative relationship with Arizona State University to use its immune system booster Viprovex with the vaccine.

Arntzen, who has also tested potato-based vaccines, noted that other teams are making plant-based vaccines.

A team at Stanford University reported last year it used tobacco to make a so-called therapeutic vaccine to treat a type of blood cancer called non-Hodgkin lymphoma.

"I would say 2009-2010 are going to be breakthrough years for plant technology in the vaccine field," Arntzen said.

He is not sure of the potential market for his vaccine.

"It probably will be an electable vaccine -- that is, adults will choose to buy it. It is not something that doctors will tell them they must have."

Hospitals, travelers and the military are potential customers, he said. Norovirus sticks to surfaces well and can live a long time unless thoroughly cleaned off.

"If someone has diarrhea and they touch a doorknob or something the next person walking through has a very good chance of picking up that disease," Arntzen said.

The technology could be applied to other vaccines, Arntzen said -- an issue that has become important as companies race to make vaccines against the new pandemic H1N1 swine flu virus. Making influenza vaccines in eggs takes five to six months.

Plants grow quickly and Arntzen said enough vaccine for clinical trials could be ready within eight to 10 weeks. Vaccine maker Novavax Inc. said on Tuesday it made its H1N1 vaccine, which uses virus-like particles grown in caterpillar cells, in four weeks.

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